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  <script>
    // 作业：数组中['老王', '老六', '老八', '雪糕老师'] 把老王和雪糕老师换个位置
    let arr =['老王', '老六', '老八', '雪糕老师']
    let sum=arr[0]
    arr[0]=arr[3]
    arr[3]=sum
    // [arr[0], arr[3]] = [arr[0], arr[3]]
    console.log(arr);
  </script>
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